#include<iostream>
#include<cmath>
using namespace std;

class Point {
    private:
        double x,y;
        friend class Line;
    public:
        Point(double x = 0,double y = 0) : x(x),y(y) {}
        Point(Point &p){
            x = p.x;
            y = p.y;
        }
};

class Line {
    private:
        Point p1,p2;
    public:
        Line(Point &p1,Point&p2):p1(p1),p2(p2) {
            
        }
        double getLenghth();
};

double Line::getLenghth() {
    double dx = p2.x - p1.x;
    double dy = p2.y - p1.y;
    return sqrt(dx * dx+dy * dy);
}

int main() {
    Point p1,p2(6,8);
    Line L1(p1,p2);
    cout << L1.getLenghth() << endl;
    return 0;
}
